This invention relates to a hinge mechanism for joining first and second members, particularly, to a hinge mechanism comprising an elastically deformable first member, a pair of pins coaxially fixed to the first member, and a second member having a recess and a pair of holes formed in the side surfaces of said recess so as to rotatably receive the pins, wherein the first member is elastically deformed so as to make the distance between free ends of the pins smaller than that between holes and, then, the external force serving to deform the first member is removed so as to put the pins in the holes formed in the side surface of said recess, thereby joining the first and second members.
In the conventional hinge mechanism of the construction described above, it is customary to produce the first and second members by injection molding of a plastic material. In general, the first member and the pins fixed thereto are molded as a single body. Likewise, the second member having a recess and holes for receiving the pins is molded as a single body. It follows that the injection mold for producing the second member is provided with a pair of projections so as to enable the produced second member to have holes serving to receive the pins fixed to the first member.
In general, the injection mold for the second member consists of a plurality of segments because the injection mold must be dismantled in releasing the injection-molded article therefrom. It should be noted in particular that the projections of the injection mold are slid along the axis thereof in releasing the produced molding. Naturally, it takes much time and labor to prepare an injection mold of such a complex structure, leading to a relatively high manufacturing cost of the injection mold. In addition, the injection mold must be assembled and dismantled each time the second member is produced, leading to a relatively low productivity. An additional difficulty to be noted is that the injection-molded article presents an unsatisfactory appearance, because the bottom surface of the recess is caused to bear scratches, which can be seen by the user of the injection-molded article, due to the effect of the projections of the injection mold which are slid along the recess in releasing the molded second member.